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Guess where?

Sometimes the things plant can tell us are more than we think.

Knowing plants can allow for an interesting trip every time we cross a green patch. We can try to read the condition of the site, the amount of rain the plant gets, the soil within its roots develop, and the main events happened there…from fires to landslides or human intrusions.

But there are cases in which plants can also tell us with a high degree of accuracy where we are. I found this astonishing! The subject that brings you to play this game is biogeography and it is more than fascinating.

Pinus nugra laricio forestThis summer I was walking my way up to an alpine lake. Along the path I met several plants that shouted loud the place where they belong.

My walk started in a pine forest, along a river. The air was fresh and moist, more than you would expect in a pine forest. The pines had high straight trunks pointing the sky and some of their traits suggested a centuries-long  life. Those trees were European black pines, but they were generally higher than those I saw before; their needles displayed some differences too.

The branches that shaded my path belong to individuals of Pinus nigra subsp. laricio. During Quaternary ice ages, European black pines spread towards southern Europan peninsulas and islands. This determined processes of isolation and diversification within the species. The subspecies laricio is native in Calabria, Sicilia and Corsica, it is particularly adapted to siliceous rocks. Looking at a lithological map of Europe its distribution definitely makes sense.

The forest ended gradually while we hiked up to the lake. Around the altitude of 1700 meters large gaps occured among the last clusters of pines. In this gaps a dwarf, thorny shrub is rather abundant. Its dominance indicates that being thorny constitutes a great advantage in this site, that is subjected to grazing during most of the year. In deed young pines could develop only around a log that protected them from grazing and trampling. Besides telling us about grazing animals we could not see in that moment, the dwarf, thorny shrub gives us another key clue to undertsand our location. It is a cushion plant of the Fabaceae family with twisted branches that end up in thorns.Genista salzmanii

It is a broom of the genus Genista. Especially the species in the picture is Genista salzmanii, it constitutes dwarf shrublands on the Mountains of Sardinia and Corsica. This species together with the Pinus nigra laricio already told us we are walking in the wonderful island of Corsica. Indeed the common name of Pinus nigra laricio is Corsican pine, and it is one of the symbols of the largest French island.

Many other species reminded me the location of my hiking, during that day; and made me wonder about the incredible diversity of Mediterranean regions.

Berberis aethnensisWhen we left behind the last pines, another dwarf thorny shrub appeared beside the path. This still had fruits on. The fruits are oval berries, coloured in red shading into yellow. It belongs to the genus named Berberis. The species of this genus that displays the widest distribution is Berberis vulgaris. But the species we met on our path does not grow higher than one meters and has thorns. In fact it is Berberis aethnensis. In some floras it is considered as a subspecies of Berberis vulgaris. Whatever its taxonomic rank, its differences with the most common taxon are evident. Berberis aethnensis is limited to Sardinia, Corsica, and south-western Italy. therefore its distribution is rather similar to the one we mentioned for the Corsican Pine.Alnus viridis suaveolens

The occurrence of Berberis aethnensis is particularly striking on the Corsican mountains because it grows right next to another shrub that usually grows at far greater latitudes, Alnus viridis, or Green Alder. In fact, while Berberis aethnensis is particularly related to the Mediterranean context, Alnus viridis is distributed in the boreal emisphere in the northern-most regions, from Alaska to Greenland and Siberia.

Alnus viridis is a light-demanding, fast-growing shrub that grows well on poorer soils, which it enriches by means of its nitrogen-fixing nodules. In many areas, it is a highly characteristic colonist of avalanche chutes in mountains, where Alnus viridis survives through its ability to re-grow from the roots and broken stumps.

Different subspecies were recognized for Green Alder in different regions; the nominate subspecies being the one developing in Central Europe (Alnus viridis viridis).

The subspecies found in Corsica is endemic to this island, that represents the most southern region of the species distribution area. The Corsican Green Alder differs from the Central European subspecies by its rounded and scented leaves, in fact it is known as Alnus viridis suaveolens (latin word for sweet-smelling) and I took home its scent through my hiking pants.

Besides trees and shrubs other tiny plants, settled on the wonderful islands of Sardinia and Corsica, that became their exclusive lands. Among those I had the pleasure to see Helicrysum frigidum and Sagina pilifera. The first one is an incredibly tiny Helicrysum (3-10 cm in height). Before landing on Corsica I thought plants belonging to this genus (family Asteraceae) were small shrubs at least half meter high. But this species growing towards the highest altitudes chose a smaller size to better resist hard windy and snowy times.

The second species I mentioned belongs to the Caryophyllaceae family. It is very similar for ecological requirements, distribution and size to Helicrysum frigidum. In the case of Sagina all the species in the genus are tiny, reaching the size of 15 cm. I found these species one next to the other and I like to think that they are linked by a friendship that already lasted for generations.

Helichrysum frigidumSagina pilifera



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